resonator design using hfss11

I am simulating a dielectric resonator antenna fed by a slot in the ground plane. Underneath the ground plane is the inverted microstrip line to couple the power from the stripline to the antenna via the slot. I am trying to simulation it using the infinite ground plane. In HFSS 10, this is easily done by just checking the "infinite ground plane" box when we assign PEC boundary condition to the ground plane. However, I'm using HFSS 11 now and I'm running into problems with this infinite ground plane. I did the same thing as in HFSS 10; however, I received the warning message telling me that the infinite ground plane does not fully touch the background. What is this message supposed to mean? Why is there a warning message in HFSS 11 while none in HFSS 10? I tried running the simulation anyway, and what I got for the far-field pattern is just the two points (theta = 90 deg and theta = -90 deg). All other points could not be calculated, thus I can't plot the radiation pattern. When I unchecked the "ininite ground plane" box (thus making it finite ground plane), everything is fine. Can anyone please help me setting up the correct infinite ground plane for my slot-coupled DRA in HFSS 11?

Thanks.

I have also meet this problem! And I have no idea about it. Could anybody explain it?